<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>FlexBoxSample</title>
    <style>
        .wrapper{
            display: flex;
            flex-direction: row;
            background-color: red;
            font-size: 24px;
            color: white;
        }
        .main{
            flex: 3;
            margin-right: 60px;
            background-color: green;
        }
        .sidebar{
            flex: 1;
            background-color: blue;
        }
    </style>
</head>
<body>
<div class="wrapper">
    <section class="main">Main section></section>
    <aside class="sidebar">Sidebar</aside>
</div>
</body>
</html>